The present invention relates to golf ball compositions that contain non-ionic polymers produced using single-site catalysts. The polymers derived using such catalysts have narrow molecular weight distributions and uniform molecular architecture. As a result of these characteristics, golf balls comprising such polymers have improved performance characteristics, such as improved distance and better control on the green.
Three-piece, wound golf balls with balata covers are preferred by most expert golfers. These balls provide a combination of distance, high spin rate, and control that is not available with other types of golf balls. However, balata is easily damaged in normal play, and, thus, lacks the durability required by the average golfer.
In contrast, amateur golfers typically prefer a solid, two-piece ball with an ionomer cover, which provides a combination of distance and durability. Because of the hard ionomer cover, these balls are almost impossible to cut. They also have a very hard xe2x80x9cfeelxe2x80x9d, however, which many golfers find unacceptable, and a lower spin rate, making these balls more difficult to draw or fade. The reduction in the spin rate can be attributed to the differences between three-piece, wound golf balls and solid, two-piece balls in the composition and construction of both the cover and the core.
Many attempts have been made to produce a golf ball with the control and feel of a wound balata ball and the durability of a solid, two-piece ball, but none have succeeded totally. For example, U.S. Pat. No. 4,274,637 to Molitor discloses two- and three-piece golf balls having covers completely or partially formed from a cellular polymeric material to improve backspin, but does not provide any examples that compare the spin rates of the disclosed golf balls with those of prior art balls.
U.S. Pat. No. 5,002,281 to Nakahara et al. discloses a three-piece solid golf ball having an ionomer cover and a solid core consisting of a soft inner core and a hard outer shell, where the difference in the hardness of the two parts of the core is at least 10 on the JIS-C scale.
Similarly, U.S. Pat. No. 4,781,383 discloses a solid, three-piece golf ball, having an ionomer cover and a core with inner and outer layers, where the inner layer has a diameter of 24 to 29 mm and a Shore D hardness of 15 to 30, and the outer layer has a diameter of 36 to 41 and a Shore D hardness of 55 to 65. The percentage of the ball surface which contacts the club face when the ball is struck is 27 to 35%.
European Patent Application 0 633 043 discloses a solid, three-piece golf ball with an ionomer or balata cover, a center core, and an intermediate layer. The center core has a diameter of at least 29 mm and a specific gravity of less than 1.4. The intermediate layer has a thickness of at least 1 mm, a specific gravity of less than 1.2, and a hardness of at least 85 on the JIS-C scale.
U.S. Pat. Nos. 5,703,166 and 5,824,746 to Rajagopalan et al. and Harris et al. disclose golf balls incorporating blends of ionomers and non-ionic polyolefin polymers produced by metallocene catalysts. Metallocene catalysts are transition metal complexes that have substituted or unsubstituted cyclopentadienyl groups serving as ligands. The polymers produced using metallocene catalysts have a narrow molecular weight distribution, and a uniform molecular architecture, such that the order and orientation of the monomers in the polymer, and the amount and type of branching is essentially the same in each polymer chain. However, metallocene catalysts technology is limited to the production of non-polar polymers. Single-site catalysts other than metallocenes, such as those disclosed herein, can produce both polar and non-polar polymers with unique properties, which will have a dramatic influence in golf ball performance.
A number of single-site catalysts other than metallocenes are known. Recent articles have disclosed several non-metallocene single-site catalysts. The Apr. 13, 1998 issue of Chemical and Engineering News describes a method a producing complexes of iron (II) and cobalt (II) with 2,6 bis-(imino)pyridyl ligands. These single-site catalysts reportedly produce polymers with narrow molecular weight distributions, and a uniform molecular architecture.
Similarly, Brookhart et al., at the Sixth International Business Forum on Specialty Polyolefins, September, 1996, reported a class of nickel (II) and palladium (II) complexes which serve as active catalysts for the polymerization of ethylene and xcex1-olefins. These complexes feature a substituted xcex1-diimine ligand. Brookhart reports that by varying, among other things, the catalyst structure the degree and type of polymer branching can be controlled.
Cribbs et al., Antec, 1998, S.P.E., discloses several single-site catalysts other than metallocene. These include diimide complexes of nickel and palladium, and complexes of 1,4,7-triazacyclononane with rhodium, chromium, and scandium. Cribbs also discloses a process for forming non-metallocene single-site catalysts that consists of deprotonating pyroles or indoles to form a monoanion, and then reacting the monoanion with TiCl4 or ZrCl4 to form the single-site catalysts. This catalyst, when co-catalyzed with a sizable excess of methylalumoxane, has been found to polymerize ethylene to narrow molecular weight distribution polyethylene. Cribbs also discloses boratabenzene complexes of the Group 4 or 5 metals, and reports that these complexes show good activity in ethylene polymerization and that the molecular weights of the product can be varied by changing the substituents on the boron atom.
In the December 1997 issue of Chemtech, Montagna discloses several examples of non-metallocene single-site catalysts, including the Brookhart catalyst and the McConville catalyst, which is a zirconium complex stabilized by diamide ligands.
International patent application PCT WO96/23010 discloses several additional single-site catalysts. These include transition metal complexes, typically nickel or palladium complexes, having an xcex1-diimine ligand.
However, although single-site catalysts are known, there is no known prior art disclosure of golf balls that incorporate compositions comprising polymers produced by such single-site catalysts, other than those produced using metallocene catalysts. Therefore, there is no appreciation in the prior art of the unique advantages obtained with golf balls produced with these materials.
While a variety of blend combinations of one species of polymer, such as ionomers, have been successfully used to make golf balls in the prior art, the prior art does not disclose successful blends of different types of polymers, such as ionomers and balata or other non-ionic polymers for use in golf ball covers. In general, prior art blends of such polymer components are immiscible, i.e., heterogeneous on a microscopic scale, and incompatible, i.e., heterogeneous on a macroscopic scale, unless strong interactions are present between the polymer components in the mixture, such as those observed between ionomers and polymers containing carboxylic acid groups. In particular, this lack of compatibility exists when an ionomer is blended with a polyolefin homopolymer, copolymer, or terpolymer that does not contain ionic, acidic, basic, or other polar pendant groups, and is not produced with a single-site catalyst. These mixtures often have poor tensile strength, impact strength, and the like. Hence, the golf balls produced from these incompatible mixtures will have inferior golf ball properties such as poor durability, cut resistance, and so on. In contrast, a compatible blend may be heterogeneous on a microscopic scale, but homogeneous on a macroscopic scale, and, thus, have useful golf ball properties.
In this regard, U.S. Pat. No. 5,397,840 to Sullivan discloses golf ball covers including a blend of xe2x80x9cionic copolymersxe2x80x9d and xe2x80x9cnon-ionic copolymersxe2x80x9d. However, the xe2x80x9cionic copolymersxe2x80x9d are defined as copolymers of an xcex1-olefin and a metal salt of an xcex1,xcex2-unsaturated carboxylic acid, and the xe2x80x9cnon-ionic copolymersxe2x80x9d are copolymers or terpolymers containing ethylene or propylene and acrylic or methacrylic acid monomers. Therefore, strong interactions exist between the metal salts of the xe2x80x9cionic copolymersxe2x80x9d and the acrylic or methacrylic acid monomers of the xe2x80x9cnon-ionic copolymersxe2x80x9d that allow compatible blends to be formed. These interactions do not exist in prior art blends of ionomers and polymers that are truly non-ionic or non-polar, in particular, those polymers produced with a process that does not involve the use of a single-site catalysts.
U.S. Pat. Nos. 4,986,545; 5,098,105; 5,187,013; 5,330,837; and 5,338,610 to Sullivan disclose golf balls having covers comprising blends of ionomers and modified thermoplastic elastomers, where the thermoplastic elastomers are conventional polymers, i.e., polymers polymerized using catalysts other than single-site catalysts. The modified polymers include maleic anhydride modified ethylene-propylene copolymers, maleic anhydride modified styrenic block copolymers, maleic anhydride modified ethylene-vinyl acetate copolymers, brominated styrene-isobutylene copolymers, amine modified ethylene-propylene rubber, and polar modified paramethylstyrene-isobutylene copolymers. However, Sullivan does not exemplify blends of ionomers with any type of modified polyolefin, including those produced with single-site catalysts. Although the disclosed balls are said to exhibit enhanced playability, i.e., softness and spin, without sacrificing coefficient of restitution and, thus, carrying distance, all of the exemplified balls have a Riehle Compression in the range of 61 to 43, which corresponds to a PGA Compression range of from 99 to 117. Therefore, even though the disclosed cover materials may be relatively soft, each of the disclosed balls has an extremely high compression, and, thus, would be expected to have a high coefficient of restitution.
As shown in U.S. Pat. No. 5,703,166, metallocene catalyzed polymers and ionomers form compatible blends having useful golf ball properties. Co-pending application Ser. No. 08/950,197 discloses golf balls comprising grafted metallocene catalyzed polymers. However, there is no known prior art disclosure of golf balls incorporating compositions comprising grafted non-metallocene single-site catalyzed polymers.
Single-site catalyzed polymers, such as those mentioned above, may be functionalized by grafting functional groups onto the polymer chain. Processes for grafting monomers onto polymers, in particular, polyolefins, are known. European Patent Application No. 0 266 994 of P. C. Wong discloses a process for grafting ethylenically unsaturated monomers, such as unsaturated carboxylic acids and anhydrides and derivatives thereof, onto copolymers of ethylene. The disclosed process comprises the steps of forming an admixture of the copolymer, the monomer, and 25 to 3,000 ppm of an organic peroxide having a half-life of from about one minute to about 120 minutes at 150xc2x0 C., and mixing the resultant admixture in an extruder at a temperature above the melting point of the copolymer for a time at least four times the half-life of the organic peroxide. The resultant grafted copolymer is then extruded into a shaped article.
U.S. Pat. No. 5,106,916 to Mitchell discloses a process for the catalytic grafting of an ethylenically unsaturated monomer onto a copolymer in which the process of EPA 0 266 994 is modified by the addition of a catalyst comprising water and at least one phosphorous-containing compound selected from the group consisting of compounds of formula HPO(OR1)2, phosphite compounds of formula P(OR2)3 and formula (OR3)Pxe2x80x94Oxe2x80x94R4xe2x80x94Oxe2x80x94P(OR5)2, and disubstituted pentaerythritol diphosphites of formula (R6O)Pxe2x80x94O2xe2x80x94RPEO2xe2x80x94P(OR7), where O2RPEO2 is the pentaerythritol moiety, and R1-R7 are specified organic functional groups.
Therefore, there is a need in the golf ball art for a golf ball formed of one or more compositions incorporating single-site catalyzed polymers, as well as blends of single-site catalyzed polymers with other polymers, including, but not limited to, ionomers. In particular, the inclusion of foamed and unfoamed, grafted or non-grafted, single-site catalyzed polymers, and blends of such polymers will allow highly durable golf balls to be produced with improved performance and virtually any combination of feel and spin rate.
The present invention is directed to golf balls having at least one layer formed of a polymer produced using a single-site catalyst, i.e., a single-site catalyzed polymer, or a blend of such polymers and one or more other polymers, such as ionomers, non-ionomeric polymers, thermoset polymers, thermoplastics, or non-single-site polymers, where the ionomer, non-ionomeric polymer, thermoplastic, or non-single-site polymer has a flexural modulus of at least about 500 psi. Typically, the at least one single-site catalyzed polymer has a hardness of at least about 15 Shore A, preferably from about 50 Shore A to about 80 Shore D, a flexural modulus of at least about 500 psi, preferably from about 1,000 to about 100,000 psi, a specific gravity of at least about 0.7, preferably from about 0.75 to about 1, a dynamic shear storage modulus (Gxe2x80x2) at 23xc2x0 C., as described in ASTM D 4092-90, ASTM D 5279-93, and ASTM D 4065-94, of at least about 104 dynes/cm2, preferably about 106 to about 1010 dynes/cm2, and most preferably from about 106 to about 109 dynes/cm2, and a loss tangent (tan xcex4) of no more than about 1, preferably, no more than about 0.1, and most preferably from about 0.001 to about 0.01. The polymer may be ionic, non-ionic, polar, or non-polar. The layer, which may have a foamed structure, forms a portion of at least one of the cover, the core, or a mantle situated between the cover and the core. Preferably, the layer further comprises at least one of a density increasing filler or a density decreasing filler. Golf balls comprising such polymers have improved performance characteristics, such as improved distance and better control on the green.
Typically, golf balls of the invention have a cover having a thickness of at least about 0.03 inch, preferably from about 0.03 to about 0.125 inch, at least about 60, preferably at least about 70 percent dimple coverage, and a hardness of from about 40 to 70 Shore D. Cores of the golf balls of the invention typically have a PGA compression of at least about 40, preferably from about 40 to about 90. Cores may be wound having a solid, gas filled, liquid filled, or hollow center that has a diameter of at least about 0.5. Optionally, the golf balls of the invention may also have a mantle situated between the cover and the core having a thickness of at least about 0.02 inch. Where the mantle is present, the core typically has a diameter of less than about 1.6 inches. The mantle may be formed from any material known in the art, including a layer formed from a wound elastomeric material. Where the layer forms at least a portion of the mantle, the mantle layer typically has a thickness of from about 0.02 to about 0.125 inch and a hardness of at least about 15 Shore D. The PGA compression of golf balls of the invention is typically in the range of from about 60 to about 120.
The present invention is generally directed in a first embodiment to golf ball compositions that comprise at least one single-site catalyzed polymer having the formula: 
wherein
R1 is hydrogen;
R2 is hydrogen or lower alkyl selected from the group consisting of CH3, C2H5, C3H7, C4H9, and C5H11;
R3 is hydrogen or lower alkyl selected from the group consisting of CH3, C2H5, C3H7, C4H9, and C5H11;
R4 is selected from the group consisting of H, CH3, C2H5, C3H7, C4H9, C5H11, C6H13, C7H15, C8H17, C9H19, C10H21, and phenyl, in which from 0 to 5 H within R4 can be replaced by substituents selected from the group consisting of COOH, SO3H, NH2, F, Cl, Br, I, OH, SH, epoxy, isocyanate, silicone, lower alkyl esters and lower alkyl ethers, with the proviso that R3 and R4 can be combined to form a bicyclic ring;
R5is hydrogen, lower alkyl including C1-C5, carbocyclic, aromatic or heterocyclic;
R6 is hydrogen, lower alkyl including C1-C5, carbocyclic, aromatic or heterocyclic; and
wherein x ranges from 100 to 50 weight per cent of the polymer, y ranges from 0 to 50 weight per cent of the polymer and z ranges from 0 to 49 weight per cent of the polymer.
The present invention is further directed in a second embodiment to golf balls having at least one foamed or unfoamed layer in at least one of the cover, the core, or in one or more intermediate mantles between the cover and the core, where the layer is formed from a composition comprising at least one single-site catalyzed polymer having a hardness of at least about 15 Shore A, a flexural modulus of at least about 500, and a specific gravity of at least about 0.7, that has optionally been functionalized by sulfonation, carboxylation, addition of an amine, hydroxy, epoxy, or isocyanate, or by grafting an ethylenically unsaturated monomer onto the at least one single-site catalyzed polymer using a post-polymerization reaction. The ethylenically unsaturated monomer is typically an olefinic monomer having a functional group selected from the group consisting of sulfonic acid, sulfonic acid derivatives, chlorosulfonic acid, vinyl ethers, vinyl esters, primary amines, secondary amines, tertiary amines, mono-carboxylic acids, dicarboxylic acids, partially or fully ester derivatized mono-carboxylic acids, partially or fully ester derivatized dicarboxylic acids, anhydrides of dicarboxylic acids, cyclic imides of dicarboxylic acids, epoxy, isocyanate, and ionomeric derivatives thereof. Preferably, the ethylenically unsaturated monomer is maleic anhydride.
Grafted single-site catalyzed polymers share the advantages of non-grafted single-site catalyzed polymers, including a narrow molecular weight distribution and uniform molecular architecture. The addition of functional groups to the single-site catalyzed polymers by grafting allows polymers to be produced having properties that are not available with unfunctionalized single-site catalyzed polymers or polymers formed without the use of single-site catalysts.
Preferably, the grafted single-site catalyzed polymer is formed by grafting an ethylenically unsaturated monomer onto a single-site catalyzed polymer selected from the group consisting of polyethylene, polypropylene, and copolymers of ethylene with propylene, butene, pentene, hexene, heptene, octene, and norbornene, most preferably, copolymers of ethylene with butene, pentene, hexene, heptene, octene, and norbornene, but may be formed by grafting an ethylenically unsaturated monomer onto any single-site catalyzed polymer of the formula: 
wherein
R1 is hydrogen;
R2 is hydrogen or lower alkyl selected from the group consisting of CH3, C2H5, C3H7, C4H9, and CH5H11;
R3 is hydrogen or lower alkyl selected from the group consisting of CH3, C2H5, C3H7, C4H9, and C5H11;
R4 is selected from the group consisting of H, CH3, C2H5, C3H7, C4H9, C5H11, C6H13, C7H15, C8H17, C9H19, C10H21, and phenyl, in which from 0 to 5 H within R4 can be replaced by substituents selected from the group consisting of COOH, SO3H, NH2, F, Cl, Br, I, OH, SH, silicone, lower alkyl esters and lower alkyl ethers, with the proviso that R3 and R4 can be combined to form a bicyclic ring;
R5 is hydrogen, lower alkyl including C1-C5, carbocyclic, aromatic or heterocyclic;
R6 is hydrogen, lower alkyl including C1-C5, carbocyclic, aromatic or heterocyclic; and
wherein x ranges from 100 to 50 weight per cent of the polymer, y ranges from 0 to 50 weight per cent of the polymer and z ranges from 0 to 49 weight per cent of the polymer.
The golf ball compositions of the invention may comprise a blend of at least one single-site catalyzed polymer, which may be functionalized, and at least one of an ionomer, a non-grafted single-site catalyzed polymer, a grafted single-site catalyzed polymer, or a non-ionomeric polymer. Any of the cover, the core, or a mantle between the cover and the core may further comprise a density increasing or decreasing filler material.